I don't think it will be terrible. I suspect that it will be an extremely bland and derivative exercise in corporate content creation, in keeping with the expectations of a consumer product with $100 million behind it.
It will be hugely successful, it will satisfy a broad range of content consumers with its thought to be risque double entendre, its thought to be smart postmodernisms, its thought to be subversive self-deprications. If you loved Barbie there will be the nostalgia tugging moment, if you didn't you can enjoy all the "oh no they didn't" take down memes.
What I don't think it will be is in any way interesting, smart, insightful or original. The Brady movie came out 30 years ago and since then there have been a constant stream of films that have ribbed, skewed, and romanticised childhood nostalgia, often with a focus towards the consumer toys market. Adam and Joe, The Karen Carpenter Story, Toy Story, Lego are just a few examples of it done with a degree of wit. It is now its own genre, and one that has become increasingly formulaic and pro-corporation. When Disney goes on a 15 minute excoriation of its own princess legacy in Wreck it Ralph 2 for a series of the lamest gags, you can see that the satire has been defanged, brought in house and controlled to within an inch of its life. Everything in the trailer is indicative of this lack of bite and imagination.
As a product it will be a hit but as a piece of filmmaking it'll be junk and just another example of corporate stodge for people to fill up on.
I don't even think that Barbie is a terrible idea for a film. Give it to a transgressive visualist with a bold vision, add an insightful script and remove it from the grip of it's owners and you could actually say something. Guffawing at the Drive guy in pastels is the other type of thing.